Magnesium base alloy



Patented June 16, 1942 UNITED STATES PATENT OFFICE MAGNESIUM BASE ALLOY No Drawing.

2 Claims.

The invention relates to magnesium base a1- loys and more particularly concerns an alloy of this nature having an exceptionally high degree of formability associated with other desirable physical properties, such as high tensile and yield strengths.

Magnesium base alloys are being widely used in the structural arts where a light weight metal is highly desirable, such as for use in making castings, forgings, and the like. However, the use of these alloys in the rolled form to make sheet metal articles requiring forming operations, such as bending, drawing, and the like, has not progressed as rapidly due to the fact that, in general, alloys having good formability or ductility permitting relatively sharp bends to be made without the article developing external Application December 23, 1940, Serial No. 371,372

that in general the preferred composition range is that in which cerium is present in an amount from aboti t 0.1 to 0.7 per cent, calcium from 0.05 to 0.5 per cent, and cadmium from 3 to '7 per cent. A particularly desirable composition because of its desirable combination of properties is one containing 0.4 per cent of cerium, 0.2 per cent of calcium, and 5 per cent' of cadmium.-

The following table, listing some of the properties of rolled sheet metal'made from my new quaternary alloy and comparing these properties with those of related parent alloys, illustrates the improvement in formability as well as yield and tensile strengths over that of related alloys. In the table the per cent elongation is to be regarded as a measure of the ductility or form;- ability of the alloys.

Table 5 9 3 compo; figf Annealed Cold rolled sium=remeindcr) Percent Yield Tensile Yield Tensile Ce Ca Cd elongation strength in strength in strength in strength in in 2 inches lbs./sq.in. lbs.lsq.in. lbe./sq.in. lbs./sq.in.

0. 5. 0 i5 16, 000 31, 0M 81, 000 36, 000 0. l1 4.9 18 17,000 33,)0 32,000 40,000 0.1 0. 24 18 20, 000 34,000 29, 000 36, 000 0.11 0. 0s a 0 21 22,000 36,000 01,000 39,000

cracks, usually have inferior characteristics as regards their tensile and yield strengths.

It is, accordingly, the principal object of the invention to provide a magnesium base alloy which can be made into rolled sheet and the like possessing a suificient degree .of ductility or formability at ordinary temperatures to be sharp.- ly bent, drawn or otherwise -shaped, while having excellent tensile and yield strengths.

Other objects and advantages will be apparent as the description of the invention proceeds.

My invention resides in the discovery that a magnesium base alloy. containing from about 0.01 to 1 per cent of cerium, from 0.01 to 1 per cent of calcium, and from 1 to- 12 per cent of cadmium possesses the aforementioned desirable properties. The term magnesium used herein and in theappended claims is intended to include magnesium containing the ordinary. impurities that are found in the commercially pure metal, such as traces of iron, copper, nickel, and silicon. While the properties of improved ductility or formability associated with high tensile and yield strengths are manifest over the entire range of composition indicated, I have found" The properties set forth above under the term annealed were obtained by first rolling the alcold rolled were obtained by subjecting speci-' mens of the alloys which had first been hotrolled at a temperature of 550 F. to'additional rolling in the cold state. The properties selected for the table were those of the cold. rolled specimens which showed the highest tensile and yield strengths, while having at least a 1 per cent elongation in 2 inches.

A comparisc i'of the properties listed in the table shows that all of the combined properties of my quaternary alloy are always superior to those of related alloys. For example, it will be noted that the new alloy shows superior elongation as well as an improvement in yield and tensile strength. This improvement is present in both the cold rolled and annealed state. Similarly, the improvement illustrated by the particular composition shown in the table is exhibited throughout the percentage range of alloying ingredients indicated.

While the new alloy is most useful in wrought form, such as sheets, due to its formability characteristics, it may also be used for making castings, extruded forms, and the like.

The new alloy may be compounded by any of the methods usually employed for melting and alloying metals with magnesium such as by adding the alloying ingredient singly or jointly to a bath of molten magnesium which is preferably protected from oxidation by suitable flux. The flux should be substantially free from magnesium chloride, if the calcium content of the alloy is above 0.3 per cent. In those instances where the alloy is to be compounded containing less than 0.3 per cent of calcium, magnesium chloride may be present in the flux, but in this case it is preferable to add the calcium last without too much stirring and agitation in .order to prevent loss of calcium into the flux. Cerium may be added to the alloy as such, or in the form of Misch-metal. Magnesium-cerium alloys are commonly made up by employing Mischmetal as a source of cerium. It is sometimes desirable to add more than the theoretical amount of Misch-metal since the alloying efliciency is not always 100 per cent and some loss may be incurred.

It is to be understood that the invention is not limited to the particular composition described herein, but may take other forms without departing from the scope of the invention.

1 claim:

1. A magnesium base alloy containing from 0.1 to 0.7 per cent of cerium, 0.95 to 0.5 per cent of calcium, and from 3.0 to 7.0 per cent of cadmium, the balance being magnesium.

2. A magnesium base alloy containing 0.4 per cent of cerium, 0.2 per cent of calcium, 5.0 per cent of cadmium, th balance being magnesium.

JOHN C. MCDONALD. 

